Surgery – Diagnostic testing
Reexamination Certificate
2000-03-03
2003-06-03
Hindenburg, Max F. (Department: 3736)
Surgery
Diagnostic testing
C600S544000, C600S508000, C600S365000, C128S920000, C128S925000
Reexamination Certificate
active
06572542
ABSTRACT:
FIELD OF THE INVENTION
This application relates to a system and method for monitoring and/or controlling patient diabetes-related blood constituents.
BACKGROUND OF THE INVENTION
The number of diabetes mellitus (DM) patients in the U.S. in 1993 was estimated to be 7.8 million persons (roughly 3.4% of the total US population). The number of patients with diabetes mellitus has steadily grown over the last 25 years (Diabetes 1996: Vital Statistics. American Diabetes Association Inc., 1996). See
FIG. 1
(U.S. Diabetes Mellitus prevalence data 1993 adapted from Diabetes Vital Statistics, American Diabetes Association 1993).
From this total, 10% (or about 0.8 million persons) are estimated to be insulin dependent diabetes mellitus (IDDM) patients. The Diabetes Control and Complications Trial (the DCCT) showed a 70% reduction in complications resulting from tight metabolic control in IDDM patients. See “The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus”, The Diabetes Control and Complications Trial Research Group, The New England Journal of Medicine, Vol. 329, No 14. Sep. 30, 1993. The DCCT underscores the importance of developing a better way to control blood glucose for the IDDM patient group. Unfortunately, the study showed substantial evidence that the frequency of hypoglycemic excursions increases 2-3 times in IDDM patients subjected to tight metabolic control compared to regular treatment. Frequent hypoglycemic excursions additionally create hypoglycemic unawareness, a state where patients become incapable of recognizing themselves the usual symptoms associated with hypoglycemia.
In the U.S. diabetes mellitus (DM) population, 90% (or 7 million persons) are estimated to be non-insulin dependent diabetes mellitus (NIDDM) patients. NIDDM patients may be subdivided into insulin users (30%, or 2.3 million persons), of which at least 25% (or 0.52 million persons) measures their blood glucose levels on a daily basis. The percentage of NIDDM patients receiving insulin treatment increases with the duration of NIDDM from 25% (0-4 years) to 60% (>20 years). It is estimated that the diagnosed number of NIDDM patients reflects only about 50% of the actual population suffering from NIDDM. However, it is recognized that only a limited percentage of this group requires improved treatment. The remainder of the NIDDM population generally self manages the disease though careful meal planning and exercise, or by means of oral hypoglycemic agents.
Comprehensive diets and injective insulin administration, combined with glucose level determination multiple times a day, may provide an acceptable degree of metabolic control, but often fall short of being optimum and may also induce considerable patient discomfort. Injected insulin does not enter the circulation directly, resulting in a delayed and reduced effect in bringing plasma glucose level down to acceptable values. Increased and prolonged hyperglycemic and/or hypoglycemic periods contribute to chronic complications. Ocular complications such as cataracts and retinopathy occur in approximately 50% of such patients after ten years. Severe nephropathy, neuropathy, and gangrene of the feet and skin complications are frequently observed.
Hypoglycemic medication, such as the sulfonylureas class of drugs, directly potentiate the release of insulin from vital pancreatic beta-cells. Severe hypoglycemia is frequently reported as a side effect of this type of drugs. More recent families of hypoglycemic agents such as biguanides and acarbose reduce the hypoglycemic threat but have a limited therapeutic scope and have undesirable side effects, which include nausea, abdominal pain and diarrhea.
A relationship between diabetes mellitus and coronary heart disease has long been suggested. See Garcia, M. J. et al., “Morbidity and Morality in Diabetics in the Framingham Population: Sixteen Year Follow-Up Study,”
Diabetes,
23:105-11 (1974); Fein, F. S., “Heart Disease In Diabetes,” Cardiovasc.
Rev. Rep.,
3:877-93 (1982); “Relationship of Glucose Tolerance to Prevalence of ECG Abnormalities and to Annual Mortality From Cardiovascular Disease: Results of the Paris Prospective Study,” Ducimetiere et al.,
J. Chron. Dis
., Vol. 32, pp. 759 to 766 (1979). Additionally, a correlation between a patient's ECG and blood potassium levels, and variations in the ECG following introductions of insulin, have been recognized. See Heine et al.,
Acta Endocrinologica
1984, 106:241-247.
The field of glucose monitoring is active. Its importance lies in indicating to the diabetic when and how much insulin should be taken. Ideally, glucose monitoring would be continuous and non-invasive. With an accurate continuously monitoring glucose sensor, information would constantly be available, either to signal a condition of hyperglycemia or hypoglycemia, or even direct and enable a closed loop system by which insulin would be automatically delivered so as to keep glucose levels close to normal physiological levels. Such a system would reduce chronic complications and provide an obvious increase in quality of life for IDDM patients.
A closed loop control system driven by a glucose sensor would enable the delivery of accurate amounts of insulin, keeping glucose levels near physiological levels while constantly monitoring upcoming hypoglycemic hazards. The key component missing in such a system is a reliable, accurate and biocompatible glucose sensor. Compared to the IDDM population, the NIDDM population is very heterogeneous in age, therapy, and stage of the disease.
Most glucose sensors presently in common use are based on electrochemical methods such as the electro-enzymatic method where blood glucose is oxidized under glucose-oxidase control, producing gluconic acid and hydrogen peroxide. By using this enzymatic reaction as a first stage, the problem is reduced to a measurement of used oxygen or produced hydrogen peroxide (i.e., the amperometric method). Alternately, the produced gluconic acid can be determined directly (i.e., the potentiometric method). Both sensor types suffer from stability problems, however. Optical glucose sensors have been experimented with, but for several reasons are not feasible for long term continuous monitoring, and especially not for implantable glucose monitoring applications.
Patents and printed publications describing various aspects of the foregoing problems and the state of the art are listed below.
U.S. Pat. No. 3,877,873 entitled “Test for Metabolic Conditions in Blood or Serum” to Winitz
U.S. Pat. No. 4,408,905 entitled “Urinary Temperature Measurement Device” to Ehrenkranz.
U.S. Pat. No. 4,476,901 entitled “Apparatus for Improving Blood Sugar Control in Diabetics” to Kraegen et al.
U.S. Pat. No. 4,776,842 entitled “Device for the Administration of Medications” to Franetzki et al.
U.S. Pat. No. 4,731,051 entitled “Programmable Control Means for Providing Safe and Controlled medication Infusion” to Fischell.
U.S. Pat. No. 4,871,351 entitled “Implantable Medication Infusion System” to Feingold.
U.S. Pat. No. 5,190,041 entitled “System for Monitoring and Controlling Blood Glucose” to Palti.
U.S. Pat. No. 5,231,988 entitled “Treatment of Endocrine Disorders by Nerve Stimulation” to Wernicke.
U.S. Pat. No. 5,368,028 entitled “System for Monitoring and Controlling Blood and Tissue Constituent Levels” to Palti.
U.S. Pat. No. 5,540,734 entitled “Cranial Nerve Stimulation Treatments Using Neurocyberetic Prostheses” to Zabara.
U.S. Pat. No. 5,741,211 entitled “System and Method for Continuous Monitoring of Diabetes-related Blood Constituents” to Renirie et al.
U.S. Pat. No. 5,844,862 entitled “Skin Temperature Radio Telemetry and Alarms” to Cocatre-Zilgien.
U.S. Pat. No. 5,919,216 entitled “System and Method for Enhancement of Glucose Production by Stimulation of Pancreatic Beta Cells” to Houben et al.
Alvestrand, A., Wahren, J., Smith, D., and DeFronzo, R. A. Insulin-mediated potassium uptake is normal in uremic and healthy subjects. Am.
J.Physiol.
246:
Houben Richard
Larik Vincent
Astorino Michael
Berry Tom G.
Hindenburg Max F.
Medtronic Inc.
Waldkoetter Eric R.
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